Question

How many moles are there in 28 grams of `CO_2`?

Answer 1

0.636 moles of CO2 or using significant figures the answer would be 0.64 moles of CO2

Explanation:

since we have a given mass of CO2 which is 28 grams and also the chemical formula of carbon dioxide (CO2) we could get the molecular mass of CO2 by using the periodic table and then when we have those information we could now get the number of moles of 28 grams of CO2.

GIVEN:
m of CO2 = 28g
Molecular Weight of C = 12 g/mol
O = 16 g/mol
To get the molecular weight of CO2 just add the molecular weights of each element and then multiply them by the number of atoms of each element. In this problem CO2, C has only one atom and O has two atoms in the compound. Therefore, getting molecular weight would be like this:
Molecular weight of CO2 = 12g/mol + 2(16 g/mol)
= 44 g/mol of CO2

Now we have the molecular weight of the compound and the given mass of compound which is 28 g. Therefore we could solve for the number of moles of CO2 in 28 g of CO2.

Using Dimensional Analysis

28g CO2 x 1 mol CO2/44g CO2 =0.636 mol of CO2

For further readings use General Chemistry by Raymond Chang 10th ed chapter 3 page 87 and for dimensional analysis chapter 1 page 27